Tag Archives: how o-rings work

O-Rings are among the simplest and most common seal types for various dynamic and static applications. The O-ring’s groove design is relatively straight forward- by sticking to properly-developed laws for groove geometry; a reliable and economical seal is obtained. When the o ring cross-section is compressed, its ability to return to its normal shape is the main reason it makes a perfect seal. Here is how o-rings work:

How they work

O-ring seals comprise of the Elastoplast circular cross section into designed O-ring groove, giving initial compression. The power needed to compress O-ring is as a result of cross section diameter and durometer. The O-ring’s seal compression is affected by its stretch by reducing cross section, which eventually lowers the sealing ability of the O-ring.

At very low or zero pressure, the natural resilience of rubber compound gives the seal. The performance of the seal can be enhanced by improving diametrical squeeze. Increasing the squeeze may lead to adverse effects in high-pressure dynamic sealing applications.

The frictional force is provided between the O-ring and the groove by the dial squeeze which holds it firmly in its installed position. The rubber compound which is engineered to deform flows up to extrusion gap. It seals it completely against leakage, till the applied pressure is sufficient enough to overcome frictional forces and deform O-ring into a smaller extrusion gap (assuming the rubber has been stretched to its limit of flow under pressure, an additional increase of force will lead to failure by extrusion or shear).

The groove has been designed to give initial force on seal across one axis ranging from 7 to 30 %. Normally this compressive force is perpendicular to that force being applied. The other axis has free volume in the groove.

When the pressure is applied, an O-ring moves towards a low-pressure side of the groove. Sealing pressure is then transmitted to the surface to be sealed, which is, in fact, higher compared to applied fluid pressure by amount same as the original interference pressure.

Increasing applied pressure leads to an interference stress between the mating surface and the seal. While the situation remains, O-ring will keep on functioning reliably and normally up to 700 pounds of force if the chosen O-ring is of the right size and the groove is properly machined to the right size.

An O-ring is perhaps the most used fluid power seal. Many people, however, fail to understand how O-rings work. O-rings can prevent leakages in almost anything right from valves and pumps to connectors and cylinders. It’s compact, economical components can handle both dynamic and static operations, in hydraulic and pneumatic applications.